lex_trace/
recorder.rs

1//! Trace recorder — implements `lex_bytecode::vm::Tracer` and builds a
2//! `TraceTree` as the VM executes.
3
4use indexmap::IndexMap;
5use lex_bytecode::vm::Tracer;
6use lex_bytecode::Value;
7use serde::{Deserialize, Serialize};
8use std::sync::{Arc, Mutex};
9
10#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
11pub struct RunId(pub String);
12
13impl RunId {
14    pub fn new(seed: &str) -> Self {
15        use sha2::{Digest, Sha256};
16        let mut h = Sha256::new();
17        h.update(seed.as_bytes());
18        h.update(format!("{:?}", std::time::SystemTime::now()).as_bytes());
19        let r = h.finalize();
20        let mut hex = String::with_capacity(64);
21        for b in r { hex.push_str(&format!("{:02x}", b)); }
22        RunId(hex)
23    }
24}
25
26#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
27#[serde(rename_all = "snake_case")]
28pub enum TraceNodeKind { Call, Effect }
29
30#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
31pub struct TraceNode {
32    pub node_id: String,
33    pub kind: TraceNodeKind,
34    /// For `Call`: the function name. For `Effect`: `kind.op` (e.g. `io.print`).
35    pub target: String,
36    pub input: serde_json::Value,
37    /// `Some` on success; `None` if the node ended in error.
38    #[serde(default, skip_serializing_if = "Option::is_none")]
39    pub output: Option<serde_json::Value>,
40    #[serde(default, skip_serializing_if = "Option::is_none")]
41    pub error: Option<String>,
42    pub started_at: u64,
43    pub ended_at: u64,
44    #[serde(default)]
45    pub children: Vec<TraceNode>,
46}
47
48#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
49pub struct TraceTree {
50    pub run_id: String,
51    pub root_target: String,
52    pub root_input: serde_json::Value,
53    pub root_output: Option<serde_json::Value>,
54    pub root_error: Option<String>,
55    pub started_at: u64,
56    pub ended_at: u64,
57    pub nodes: Vec<TraceNode>,
58}
59
60impl TraceTree {
61    /// Find a node by `NodeId`, depth-first.
62    pub fn find(&self, node_id: &str) -> Option<&TraceNode> {
63        for n in &self.nodes {
64            if let Some(found) = find_in(n, node_id) { return Some(found); }
65        }
66        None
67    }
68}
69
70fn find_in<'a>(n: &'a TraceNode, target: &str) -> Option<&'a TraceNode> {
71    if n.node_id == target { return Some(n); }
72    for c in &n.children {
73        if let Some(f) = find_in(c, target) { return Some(f); }
74    }
75    None
76}
77
78/// Tracer that builds a `TraceTree`. The tree is shared via `Arc<Mutex>`
79/// so callers can read it after the VM finishes.
80pub struct Recorder {
81    state: Arc<Mutex<RecorderState>>,
82}
83
84pub(crate) struct RecorderState {
85    /// Open frames: each entry has its inputs filled in but `output`/
86    /// `error`/`ended_at` not yet known. Children of an open frame are
87    /// staged into a sibling buffer; on `exit`, they get attached to the
88    /// node that's closing.
89    open: Vec<OpenFrame>,
90    /// Top-level finished nodes (the call we're tracing might span the
91    /// whole VM run, so this is normally a single node tree).
92    completed: Vec<TraceNode>,
93    /// Effect overrides for replay; keyed by NodeId.
94    pub(crate) overrides: IndexMap<String, serde_json::Value>,
95}
96
97struct OpenFrame {
98    node: TraceNode,
99    /// Children that have completed under this frame.
100    children: Vec<TraceNode>,
101}
102
103impl Recorder {
104    pub fn new() -> Self {
105        Self {
106            state: Arc::new(Mutex::new(RecorderState {
107                open: Vec::new(),
108                completed: Vec::new(),
109                overrides: IndexMap::new(),
110            })),
111        }
112    }
113
114    /// Returned handle stays valid after the tracer is moved into the VM.
115    pub fn handle(&self) -> Handle {
116        Handle { state: Arc::clone(&self.state) }
117    }
118
119    /// Pre-load effect overrides for replay.
120    pub fn with_overrides(self, overrides: IndexMap<String, serde_json::Value>) -> Self {
121        self.state.lock().unwrap().overrides = overrides;
122        self
123    }
124}
125
126impl Default for Recorder { fn default() -> Self { Self::new() } }
127
128#[derive(Clone)]
129pub struct Handle {
130    state: Arc<Mutex<RecorderState>>,
131}
132
133impl Handle {
134    /// Drain the recorder into a finished `TraceTree`. Call after the VM
135    /// run returns. `root_target` and `root_input` describe the top-level
136    /// call (e.g. the `lex run` entry).
137    pub fn finalize(
138        &self,
139        root_target: impl Into<String>,
140        root_input: serde_json::Value,
141        root_output: Option<serde_json::Value>,
142        root_error: Option<String>,
143        started_at: u64,
144        ended_at: u64,
145    ) -> TraceTree {
146        let st = self.state.lock().unwrap();
147        TraceTree {
148            run_id: RunId::new(&format!("{}-{}", started_at, ended_at)).0,
149            root_target: root_target.into(),
150            root_input,
151            root_output,
152            root_error,
153            started_at,
154            ended_at,
155            nodes: st.completed.clone(),
156        }
157    }
158}
159
160fn now_unix() -> u64 {
161    use std::time::{SystemTime, UNIX_EPOCH};
162    SystemTime::now().duration_since(UNIX_EPOCH).map(|d| d.as_secs()).unwrap_or(0)
163}
164
165fn values_to_json(args: &[Value]) -> serde_json::Value {
166    serde_json::Value::Array(args.iter().map(value_to_json).collect())
167}
168
169fn value_to_json(v: &Value) -> serde_json::Value {
170    use serde_json::Value as J;
171    match v {
172        Value::Int(n) => J::from(*n),
173        Value::Float(f) => J::from(*f),
174        Value::Bool(b) => J::Bool(*b),
175        Value::Str(s) => J::String(s.to_string()),
176        Value::Bytes(b) => J::String(b.iter().map(|b| format!("{:02x}", b)).collect()),
177        Value::Unit => J::Null,
178        Value::List(items) => J::Array(items.iter().map(value_to_json).collect()),
179        Value::Tuple(items) => J::Array(items.iter().map(value_to_json).collect()),
180        Value::Record(fields) => {
181            let mut m = serde_json::Map::new();
182            for (k, v) in fields { m.insert(k.clone(), value_to_json(v)); }
183            J::Object(m)
184        }
185        Value::Variant { name, args } => {
186            let mut m = serde_json::Map::new();
187            m.insert("$variant".into(), J::String(name.clone()));
188            m.insert("args".into(), J::Array(args.iter().map(value_to_json).collect()));
189            J::Object(m)
190        }
191        Value::Closure { body_hash, .. } => {
192            // Render the first 4 bytes (8 hex chars) of the body hash
193            // (#222). Equivalent closures across source locations now
194            // produce the same trace token, so trace replay is stable
195            // when a developer moves a closure literal.
196            let prefix: String = body_hash.iter().take(4)
197                .map(|b| format!("{b:02x}")).collect();
198            J::String(format!("<closure {prefix}>"))
199        }
200        Value::F64Array { rows, cols, data } => {
201            let mut m = serde_json::Map::new();
202            m.insert("$f64_array".into(), J::Bool(true));
203            m.insert("rows".into(), J::from(*rows));
204            m.insert("cols".into(), J::from(*cols));
205            m.insert("data".into(), J::Array(data.iter().map(|f| J::from(*f)).collect()));
206            J::Object(m)
207        }
208        Value::Map(m) => {
209            let mut o = serde_json::Map::new();
210            o.insert("$map".into(), J::Bool(true));
211            o.insert("entries".into(), J::Array(m.iter().map(|(k, v)| {
212                J::Array(vec![value_to_json(&k.as_value()), value_to_json(v)])
213            }).collect()));
214            J::Object(o)
215        }
216        Value::Set(s) => {
217            let mut o = serde_json::Map::new();
218            o.insert("$set".into(), J::Bool(true));
219            o.insert("items".into(), J::Array(
220                s.iter().map(|k| value_to_json(&k.as_value())).collect()));
221            J::Object(o)
222        }
223        Value::Deque(items) => {
224            let mut o = serde_json::Map::new();
225            o.insert("$deque".into(), J::Bool(true));
226            o.insert("items".into(), J::Array(
227                items.iter().map(value_to_json).collect()));
228            J::Object(o)
229        }
230        Value::Actor(_) => J::String("<actor>".into()),
231        Value::ArrowTable(t) => {
232            // Trace records the *shape*, not the data — full Arrow tables
233            // can be GB-scale. Replay through the agent API doesn't need
234            // the rows; if it does, capture them via `arrow.row_at`.
235            let mut o = serde_json::Map::new();
236            o.insert("$arrow_table".into(), J::Bool(true));
237            o.insert("nrows".into(), J::from(t.num_rows() as i64));
238            o.insert("ncols".into(), J::from(t.num_columns() as i64));
239            J::Object(o)
240        }
241    }
242}
243
244pub(crate) fn json_to_value(v: &serde_json::Value) -> Value {
245    use serde_json::Value as J;
246    match v {
247        J::Null => Value::Unit,
248        J::Bool(b) => Value::Bool(*b),
249        J::Number(n) => {
250            if let Some(i) = n.as_i64() { Value::Int(i) }
251            else if let Some(f) = n.as_f64() { Value::Float(f) }
252            else { Value::Unit }
253        }
254        J::String(s) => Value::Str(s.as_str().into()),
255        J::Array(items) => Value::List(items.iter().map(json_to_value).collect()),
256        J::Object(map) => {
257            // Detect the $variant shape we emit on the way out.
258            if let (Some(serde_json::Value::String(name)), Some(serde_json::Value::Array(args))) =
259                (map.get("$variant"), map.get("args"))
260            {
261                return Value::Variant {
262                    name: name.clone(),
263                    args: args.iter().map(json_to_value).collect(),
264                };
265            }
266            let mut out = indexmap::IndexMap::new();
267            for (k, v) in map { out.insert(k.clone(), json_to_value(v)); }
268            Value::Record(out)
269        }
270    }
271}
272
273impl Tracer for Recorder {
274    fn enter_call(&mut self, node_id: &str, name: &str, args: &[Value]) {
275        push_call_frame(&self.state, node_id, name, args);
276    }
277    fn enter_effect(&mut self, node_id: &str, kind: &str, op: &str, args: &[Value]) {
278        push_effect_frame(&self.state, node_id, kind, op, args);
279    }
280    fn exit_ok(&mut self, value: &Value) { exit_ok_frame(&self.state, value); }
281    fn exit_err(&mut self, message: &str) { exit_err_frame(&self.state, message); }
282    fn exit_call_tail(&mut self) { exit_tail_frame(&self.state); }
283    fn override_effect(&mut self, node_id: &str) -> Option<Value> {
284        lookup_override(&self.state, node_id)
285    }
286}
287
288/// Tracer impl for the recorder's shareable handle (#199). Multiple
289/// `Vm` instances driven against the same `Recorder` — for example,
290/// the spec-checker's per-`SpecExpr::Call` Vms — can each take their
291/// own `Box<dyn Tracer>` cloned from this handle, and the events
292/// will fold into the same trace tree.
293impl Tracer for Handle {
294    fn enter_call(&mut self, node_id: &str, name: &str, args: &[Value]) {
295        push_call_frame(&self.state, node_id, name, args);
296    }
297    fn enter_effect(&mut self, node_id: &str, kind: &str, op: &str, args: &[Value]) {
298        push_effect_frame(&self.state, node_id, kind, op, args);
299    }
300    fn exit_ok(&mut self, value: &Value) { exit_ok_frame(&self.state, value); }
301    fn exit_err(&mut self, message: &str) { exit_err_frame(&self.state, message); }
302    fn exit_call_tail(&mut self) { exit_tail_frame(&self.state); }
303    fn override_effect(&mut self, node_id: &str) -> Option<Value> {
304        lookup_override(&self.state, node_id)
305    }
306}
307
308// ---- Tracer body, factored so Recorder and Handle share it. ------
309
310fn push_call_frame(state: &Mutex<RecorderState>, node_id: &str, name: &str, args: &[Value]) {
311    let mut st = state.lock().unwrap();
312    st.open.push(OpenFrame {
313        node: TraceNode {
314            node_id: node_id.to_string(),
315            kind: TraceNodeKind::Call,
316            target: name.to_string(),
317            input: values_to_json(args),
318            output: None,
319            error: None,
320            started_at: now_unix(),
321            ended_at: 0,
322            children: Vec::new(),
323        },
324        children: Vec::new(),
325    });
326}
327
328fn push_effect_frame(state: &Mutex<RecorderState>, node_id: &str, kind: &str, op: &str, args: &[Value]) {
329    let mut st = state.lock().unwrap();
330    st.open.push(OpenFrame {
331        node: TraceNode {
332            node_id: node_id.to_string(),
333            kind: TraceNodeKind::Effect,
334            target: format!("{kind}.{op}"),
335            input: values_to_json(args),
336            output: None,
337            error: None,
338            started_at: now_unix(),
339            ended_at: 0,
340            children: Vec::new(),
341        },
342        children: Vec::new(),
343    });
344}
345
346fn exit_ok_frame(state: &Mutex<RecorderState>, value: &Value) {
347    let mut st = state.lock().unwrap();
348    if let Some(mut frame) = st.open.pop() {
349        frame.node.ended_at = now_unix();
350        frame.node.output = Some(value_to_json(value));
351        frame.node.children = frame.children;
352        attach_completed(&mut st, frame.node);
353    }
354}
355
356fn exit_err_frame(state: &Mutex<RecorderState>, message: &str) {
357    let mut st = state.lock().unwrap();
358    if let Some(mut frame) = st.open.pop() {
359        frame.node.ended_at = now_unix();
360        frame.node.error = Some(message.to_string());
361        frame.node.children = frame.children;
362        attach_completed(&mut st, frame.node);
363    }
364}
365
366fn exit_tail_frame(state: &Mutex<RecorderState>) {
367    let mut st = state.lock().unwrap();
368    if let Some(mut frame) = st.open.pop() {
369        frame.node.ended_at = now_unix();
370        frame.node.output = Some(serde_json::Value::Null);
371        frame.node.children = frame.children;
372        attach_completed(&mut st, frame.node);
373    }
374}
375
376fn lookup_override(state: &Mutex<RecorderState>, node_id: &str) -> Option<Value> {
377    let st = state.lock().unwrap();
378    st.overrides.get(node_id).map(json_to_value)
379}
380
381fn attach_completed(st: &mut RecorderState, node: TraceNode) {
382    if let Some(parent) = st.open.last_mut() {
383        parent.children.push(node);
384    } else {
385        st.completed.push(node);
386    }
387}
lex_trace/recorder.rs

lex_trace/
recorder.rs
